On the last two weeks, I flew in DL 757 once and DL767 three times. Last month I flew in a CO 767. None of pilots applied thrust reverse on landing. I believe they used autobrakes and idle reverse. Why are they doing that? Saving engine life?. Don't need reverse at all? Noise issues?. (I love the noise on those engines when reverse is applied and I was quite dissapointed on my last flights because everything was so quiet.) Does anyone has an explanation??

There are airports where idle reverse is requested (noise) unless required to be used for the braking of the aircraft... I often land on airports (MAD) where we have to exit the runway at the end of a long runway... we just deploy the reversers (to cancel residual trust) - not even using the wheel brakes until slowed to 80 knots or so... would be ridicululous to stop the airplane in 6,000 feet, then add power to expedite or reach the exit at the end...
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I am sorry, Vh320, if this does not please you... "me" is pilot, "you" is passenger...
End of my comments...
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Happy contrails (s) Skipper

Thank you for your explanation skipper. About my comment regarding dissapointment because I did not listen the engines common sound when reverse is applied was, that is just an "aviation fan" comment. That "me" is pilot, "you" is passenger sound like an agressive answer. No more comments...

Dear Vh320 -
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My apologies to you... I did not meant to be like that...
Just that here in Tech.Ops. we are accustomed to "just technical" comments...
The "airline with sexiest F/As" and equivalents, normally go in "Civ.Av."...
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I guess I must have blown my fuse yesterday...
Wife had a severe case of PMS...
Welcome by the way, I see you are new with us...
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Happy contrails (s) Skipper

I know that it is the policy at American Eagle (at least on the Embraers) to not use reverse thrust on runways 7000 feet or greater in length. It is fuel conservation issue as the aircraft has a great carbon brake system that can take a lot of heat easily.

I don't know what kind of Delta B767 you were flying, but Continental's 767s (both -200/400) use carbon brakes. Older 767s do not use carbon brakes. I would assume that Delta's 767-400s use them.
Procedures are for idle reverse only (conditions permitted obviously) because of the differences between carbon and steel brakes. Steel brakes wear more with high temps. Carbon brakes are much more effective when at high temps. They wear less with a constant smooth application. Steel brakes are the opposite. So on the Co 767s, idle reverse thrust will be used. It is actually a much smoother landing especially with autobrakes used.

That is why higher reverse thrust settings are used on aircraft with steel brakes.

Here is further reading:

Operational usage and life testing of carbon brakes
has revealed that carbon brakes wear out at different
rates than steel brakes. A Re-jected
Take Off (RTO), as described at the open-ing
of this document, dumps massive heat en-ergy
into the brake, and would be expected to
be the “worst case” for brake wear. Carbon
surprisingly shows much less wear than
steel under these con-ditions. But during
normal taxi operations, carbon wore at much
higher rate-more com-parable to steel.
In research and testing to study this differ-ence,
it was found that with a steel brake, the
amount of wear on the brake generally corre-lated
to how much en-ergy was absorbed by the brake.
Carbon friction materials exhibited
wear as a function of the number of applica-tions,
not just the total energy. In other words,
it is better to apply brakes continuously and
smoothly than to apply and release, apply and
release, etc. There is also data showing that
carbon wears less at high temperatures.

No difference with automobiles really in regards to carbon brakes from what you have posted above, that is, they don't work well unless they are hot. I had them on an BMW I used to autocross and they were terrible until I warmed em up real good.

Dear Vh320 -
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I compare "passengers telling me how to handle the plane" similtar to, or equal to your mother-in-law telling you how to handle your car in traffic...
Pilots do strange things, in the opinion of the travelling public, when they operate aircraft. It is dictated by procedures and many restrictions imposed upon them. When I fly my plane, whether a 747 (which does not belong to me), and my little toy plane (L-21) which belongs to me... thinking of (1) safety (2) wear and tear of that airplane (3) economy (4) passenger confort and convenience...
Besides, I hate my mother-in-law. My next car will be a Miata...
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Happy contrails (s) Skipper

I read an article "recently" (18 months ago) about break technology, that has evolved tremendously in the last years.

So much so that, according to that article, Airbus' first offer of the A380 did not include thrust reversers, in order to save some weight, relying only on the brakes to slow down the giant plane. It's only under clients pressure that Airbus has decided to offer thrust reversers, only on 2 engines though.